Self-clamping jack



1 G. L. DU ROSTU 2,252,494

SELF-CLAMPING JACK Filed May B, 1946 4 Sheets-Sheet l n; :2: W 8 6 I 5 62 64 Au 12, 1941. G. L. DU ROSTU SELF-CLAMPING JACK 4 Sheets-$het 2 Filed May 8, 1940 Aug? 1941- G. L. DU ROSTU 2,252,494

SELF-CLAMPING JACK Filed May 8, 1940. 4 Sheets-Sheet 3 G. L. DU ROSTU SELF Aug. 12,. 1941.

-CLAMPING JACK Filed May 8, 1940 4 Sheets-Sheet 4 9 EDEGGEEGGEEEEEEEEEGE EEEQEQEEEGEEE 2 a ti-anmmi, I

Patented Aug. 12, 1941 SELF-CLAMPING JACK Georges Levesque du Rostu, Paris, France, as-

signor to Socit Anonyme: Andre Citroen, Paris (Seine), France Application May 8, 1940 Serial No. 334,074 In France May 20, 1939 5 Claims.

In self-clamping jacks, the movable part is arranged in such a manner that the load it receives is transmitted in overhanging position, more or less directly to a unit forming a clamping ring along the lifting rod or column. This clamping is finally effected by two ridges which cut more or less into the rod and have, moreover, the inconvenience of wearing very rapidly, so that the lowering operation becomes very difficult to control and is often converted into a free drop.

The present invention has for an object a self-clamping jack in which the clamping ridges are replaced by small surfaces which brake and stop the movement lowering the load, and the system controlling the movable part, constituting a lever and link connection, allows, of effecting a positive control of the lifting and of the lowering, whilst utilising for forming the friction or wedging members materials of relatively slight superficial hardness.

Said wedging surfaces, which can be plane or cylindrical of any profile, press against the plane or rounded edges of the flanges of a vertical beam of I-shaped cross section; they are preferably obtained by milling portions formed in two small horizontal spindles held on either side of the beam by means of a fork member on which they are mounted at different levels.

This fork member receives the load on one side only, that corresponding to the lower spindle, which produces its clamping on the beam. In the web of said beam are formed, along its axis and at right angles thereto, a series of rectangular perforations having flat edges, equal distances apart, in which can engage the teeth carried by the end of thedever adapted to produce the lifting or the lowering of the load, by successive rocking movements. This arrangement insures that once the teeth of the lever are engaged in the corresponding holes they do not escape therefrom under the influence of the load when the lever is rocked in one direction or in the other, according as the load is lifted or lowered.

When the lever, located in such a manner that its teeth mesh with the perforations of the supporting rod above the fork; is pulled upwardly, it unclamps the fork then lifts the load, through the medium of links then acting on the lower spindle of the fork. When the lever, located in such a manner that its teeth mesh with the perforations of the supporting rod below the fork, is pushed downwardly, it allows the load to be lowered by unwedging the fork through the medium of other links acting on the higher spindle of the latter.

Another feature of the invention consists in that .the web of the beam, slotted at its lower part and spread out in V shape is pivoted on a resilient base taking a bearing on the ground. This arrangement is particularly advantageous when the jack is used for lifting a car stopped on a slope. In fact, the pivotal joint allows the supporting rod to take the required inclination.

In the accompanying drawings, by way of example:

Fig. 1 shows the self-clamping device and means actuating the movable part.

Figs. 2 to 6 illustrate a first form of construction.

Fig. 2 is a vertical section made according .to II-II of Fig. 3.

Fig. 3 is a cross section made according to III-I1I of Fig. 2.

Fig. 4 is a side view.

Figs. 5 and 6 illustrate in front view and side view the central rod and the base.

Fig. 7 illustrates a second embodiment, seen in section in the same conditions as Fig. 3.

According to the embodiment shown in Figs. 2 to 6, a central rod l of I cross section has two plane surfaces la and lb on which bear plane milled portions formed in two small round spindles 2a and 22) parallel to each other, at right angles to the medium plane of the rod I and pivotally mounted in a fork 3 on one side of which bears the load.

The fork 3 is made for instance of thick sheet metal folded in U shape, in the branches of which are freely inserted without play the spindles 2a and 2b vertically offset relatively to each other. The assembly thus obtained can slide along the central rod.

Under the effect of the load, the fork 3 rocks slightly, drawing along the spindles, which causes it to be clamped along the beam. The greater the load, the more the spindles press against the flanges, always presenting their plane portions against the plane faces Ia and lb owing to their mobility about their geometrical axes.

The area of the surfaces in contact and the spacing apart in the vertical plane of the clamping forces generated which pass through the geometrical axes of the spindles 2a and 2b, are determined according to the weight of the load to be lifted.

In order that the whole structure should not slide under its own weight, a slight clamping is permanently obtained by the action of a spring 4 wound about the spindle 2a and having, on the one hand, two branches pressing against the web of the beam l (at the origin of the flanges), and on the other hand, a tail piece passing through a hole 3 perforated in the base of the U of the fork 3; this latter branch acts on the fork in the same direction as the load to be lifted.

In the example illustrated, the load being applied on the side where the spindle 2a is located, it is the latter which must be lifted for raising the load. If, on the contrary, the operation is effected by lowering the spindle 2b, the clamping tends to be reduced, so that it is the load which causes the movable part to lower until, the action on the spindle 21) being interrupted, self-clamping takes place again instantaneously, either under the action of the load, or under that of the spring 4.

For obtaining these results, two lifting links (Figs. 1, 2 and 4) located on the outer sides of the fork 3, are pivoted on either side of the spindle 2a and retained by pins (5-; moreover, the spindle 2b freely passes through a member 1 located between the flanges of the beam I, and. carrying two arms such as B forming lowering links.

In the web of the beam l are provided at regular intervals and at right angles to its axis, rectangular perforations 9, in which can enter one or more teeth Ii) of suitable profile, carried by the end of a control lever ll pivoted between the links 8 on a spindle I2 parallel to the spindles 2a and 2b.

The links 5 and 8 are provided, at their ends with slots 5a and 8a through which passes said spindle l2; on the latter are threaded small stay members such as [3 the cheeks of which maintain the space separating the links 5 and 8 and which act as rollers for rolling along the flanges of the beam, when lifting and when lowering the load; finally, two pins I4 located on either side of the links 5 complete this assembly.

For effecting the lifting of the load, the spindle [2 of the lever is brought into its upper position relatively to the fork 3 (Fig. 2); the lever is acted upon by pulling it upwardly. Taking a bearing by means of its teeth H) in the perforations 9 of the supporting rod I, it transmits the stress in the same manner as a lever of the second type by lifting the spindle l2. The latter slides in the slots 50: and 8a which are so shaped that it reaches the top of the slots 5a without being at the top of the slots 8a. Therefore, the links 8 are not used during the lifting of the load. The spindle l2 transmits its lifting movement through the links 5 to the spindle 2a which first produces the unclamping of the fork, then the lifting of the load.

When the lever has reached the limit of its angular upward position, it is moved away by disengaging the teeth from the perforations of the supporting rod, it is caused to rotate about the spindle I2 until it is placed at the limit of its angular downward position and it is moved towards the supporting rod by meshing its teeth in the perforations of the latter. It is then possible for the lever to effect another stroke. Successive lifting movements are thus effected until the load is lifted to the desired height.

For controlling the lowering of the load, the spindle l2 of the lever being brought into its lower position relatively to the fork 3 (position shown in clot and dash lines in Fig. 2), the lever is acted upon by lowering it. The slots 5a, 8a are such that, in this case, the links 8 are the only ones which act. Through the medium of said links, the spindle I2 causes the spindle 2b to lower which produces the unclamping of the fork 3 and allows, consequently the load to be lowered.

In the same manner as for the lifting, when the lever has reached its lower position, it is moved away so that it can be brought in mesh in its upper position, and so on.

It is advantageous that the system of links 5 and 8 should be maintained in the upper position. A simple arrangement consists in causing the spindle 2b to slightly extend on either side of the fork 3 so that, as they are provided with two external rounded portions, the lifting links are stopped by these two ends forming bosses. For passing to the lower position, it suffices to exert a slight downward pressure for moving the links 5 slightly apart owing to their resiliency.

Another arrangement consists in internally perforating the links 8, and in interposing in the holes, between the spindles 2b and I2 two small coil springs diagrammatically illustrated at [6, Figs. 2 and 4; these springs, in lifting position, hold the spindle I2 constantly in contact with the active portion of the slots of links 5, whereas in lowering position they hold it against the active portion of the slots of links 8.

The foot of the jack is advantageously formed in the following manner:

The web of the beam, slotted at its lower part according to its axis, forms the two branches l1 and I1 of a V the ends of which are rigidly connected by a cross member l8, for instance of channel shape which rests on a resiliently distortable base l9 (Figs. 5 and 6).

Seen in plan view, said base has a rectangular shape; seen in section, it has, according to its long sides, two downwardly inclined edges 28 and, according to its long axis a median flared roove 2| at the bottom of which rest-s the channel [8.

Finally, half-rings 22 passing over the channel l8 and hooking in the base l9 form the pivotal joints allowing the beam to freely rock in the angle of the groove 2!. This assemblage is not rigid, and the rings 22 can be simply constituted, according to the example chosen, by two curved and slotted pins.

Said pins, placed near the feet of the central rod, hold it in the longitudinal direction and prevent it from sliding on the base [9 when the latter is inclined according to its long axis, in particular when the jack is used at the side of a car located on a slope.

For using the jack in a general manner, it sufiices to secure to the load an iron member such as 23 terminating in a flat edge and curved so that it can be engaged above the U of the fork. In the case of a motor car, the assemblage of such an iron member capable of being easily dismantled can be devised, and it can be secured for instance on a footboard near a wheel to be repaired; but it is often more simple to arrange several iron members of this kind permanently mounted on the car body near the wheels and at the middle of the car. This arrangement allows of lifting either each wheel separately or the entire side of the car.

In these conditions, the jack will first of all relieve the suspension and will then lift the wheel or wheels; the height of the central beam must of course be proportioned to the kind of vehicle to be lifted.

As soon as the jack is loaded, the resilient base forming a spring lowers, its central part 2| touching the ground whereas the edges 20 become firmly anchored therein. In proportion as the movable part rises, the beam inclines, and there is no danger Whatever of the load escaping therefrom, which often occurs with certain jacks if special precautions are not taken.

Furthermore, a single jack provided with a base according to the invention allows of lifting. a side of the car sufficiently high for allowing easy access to the lower members.

The embodiment which has just been described is given only by way of example and, the forms, proportions and arrangement of the various members can be varied without departing from the invention; in particular, the central rod can have any cross section other than an I. The member '!B--8 the machining of which is somewhat complicated, can be made in three parts, and in this case the lowering links can be given a smaller thickness and even, for further lightening the movable part, they can be made of sheet metal as the links 5 and directly mounted on the spindle 2b. Fig. 7 shows an embodiment of the jack according to this latter modification and with a central rod made of sheet metal, the whole constituting an economical, rugged and light apparatus.

The rod 24 is hollow and has an I-shaped cross section the edges of the flanges of which are rounded according to a portion of an arc of circle having a radius R. This cross section can be easily obtained by means of a tube made of sheet metal rolled and welded, which is then subjected to one or two shaping processes by means of a roller or by a drawing operation.

The spindles 25a. and 25-h press against the edges of the flanges through milled portions the radius of which R-I-e is slightly greater than the radius B. This slight difference of radius allows of advantageously utilising the resiliently distortable property of the walls of the beam 24. In fact, in the absence of any load, the milled portions of the clamping spindles can rest on the edges of the beam by bearing on a very restricted surface. But when the load is applied, the spindles 25a and 25b pressing against the flanges of the beam I, distort them, and the zones of contact increase until the forces in action balance each other.

I claim:

1. .A self-clamping jack comprising an upright having a rack, a fork adapted to slide along said upright, two spindles pivotally mounted in the cheeks of said fork, at slightly different levels and adapted to press against twoopposite sides of said upright, a lever terminated by a toothed segment adapted to mesh with the rack of the upright, a transverse spindle on said lever and links connecting said transverse spindle res-pectively to the two spindles mounted in said cheek, the pivotal joint of each of said links being so devised that said link has a certain amount of play in the longitudinal direction on said transverse spindle.

2. A jack as claimed in claim 1, the upright of which has an I-shaped cross section and the spindles of which mounted in the fork have notches adapted to press against the edges of the flanges of said upright through surfaces sufficiently wide so that said edges are practically not penetrated by said spindles under the action of the loads which said fork is intended to support.

3. A jack as claimed in claim 1, in which the spindle mounted on the side of the fork adapted to support the loads is located slightly lower than the spindle mounted on said fork on the opposite side relatively to the upright.

4. A jack as claimed in claim 1, in combination with a base constituted by a plate made of resilient metal the-middle of which is curved in the shape of a channel to receive the base of the upright, and the edges of which parallel to said channel are downwardly bent, and means for retaining the base of the upright in said channel Whilst allowing it to rock,

5. A jack as claimed in claim 1, the upright of which is constituted by a sheet metal member curved on itself according to an I profile having hollow flanges and rounded angles, the spindles mounted on the sliding fork having channel shaped notches adapted to engage on the edges of said flanges, the radius of curvature of the profile of said notches being very slightly greater than the radius of curvature of the profile of the edges of the flanges.

GEORGES LEVESQUE DU ROSTU. 

